March 22, 2010 -- A CDC investigation shows a measles outbreak in San Diego was fueled by kids whose parents refused to vaccinate them,
thus endangering children too young to be vaccinated.

Measles is one of the world's most highly contagious viral diseases. Thanks to high vaccination rates, the dangerous disease stopped circulating in the
U.S. But now there are ominous signs it may come back.

The reason: Pockets of parents who believe the measles/mumps/rubella (MMR) vaccine is more dangerous than the diseases. Such beliefs led to a drop-off in MMR
vaccination in England -- and the subsequent return of measles.

Could it happen in the U.S.? Yes, suggests an in-depth study of the 2008 measles outbreak in San Diego.

San Diego Measles Outbreak

The outbreak began in January 2008 when a 7-year-old boy whose parents refused to vaccinate him returned to the U.S. from Switzerland. Before symptoms
appeared, he infected his 3-year-old brother and 9-year-old sister. Neither was vaccinated.

Neither were 11% of the boy's classmates, whose parents shared similar beliefs that a healthy lifestyle protected against disease while vaccines were
riskier than the illnesses they prevented.

In the end, 839 people were exposed to measles. Eleven were infected, and 48 exposed kids too young to be vaccinated were quarantined -- forbidden to leave
their homes -- for 21 days. Jane Seward, MBBS, MPH, was the CDC's senior investigator for the outbreak.

"Even with the very high vaccine coverage that we saw in San Diego, if you have a community of vaccine refusers you can get an outbreak," Seward tells
WebMD. "Had the local health department not been extremely aggressive in quarantining everyone who came in contact with a case who did not have
immunity, the outbreak would have broadened."

Fortunately, nobody died or suffered neurological damage. But there was one very close call.

Megan Campbell's 10-month-old son was in the pediatrician's waiting room when the boy who'd been infected in Switzerland came in. The infant got very, very sick --
so sick that Campbell and her family thought he was going to die.

"There were moments I was worried he wouldn't make it because this fever just wasn't letting up. This 106-degree fever, and this rash that made my son look
like an alien almost, and I wondered if he was going to be the same boy he was a week before," Campbell told interviewer Susan Burton on the radio program
This American Life.

The infant spent three days in the hospital. He dropped from 18 to 12 pounds in five days. He was sick for weeks; Campbell and her husband had to take a
month off of work. Fortunately, the boy recovered fully.

"I just wondered how this family who had brought this into San Diego, what were they thinking?" Campbell said on the radio program. "Were they thinking
they were part of something that put that child there? Did they feel for us at all? Did they feel bad about it?"

Many Parents Question Vaccine Safety

Part of the CDC and San Diego County investigation involved outreach to parents in the affected community who believe vaccines pose a greater risk to
children than the diseases they prevent.

These parents told the researchers that they were skeptical of vaccine safety and efficacy claims by the government, the pharmaceutical industry, and
the medical community. They felt there was a very low risk of getting a vaccine-preventable disease, and that such diseases were better prevented by
"natural lifestyles" including prolonged breastfeeding and organic foods. Most felt vaccines could damage a child's immune system and cause
neurologic complications such as autism.

"I really don't think many of them changed their minds," study investigator and CDC researcher Albert E. Barskey, MPH, tells WebMD. "They were pretty set
in their ways. In fact, when given the choice of vaccinating their children after exposure so they could go back to school, most chose instead to keep them
quarantined at home for three weeks."

Even so, when faced with the fact that their children had been exposed to measles, about 40% of the parents did chose vaccination over quarantine.

Vaccine Debate Rages On

Despite the extraordinary efforts of health workers, what really ended the San Diego outbreak wasn't quarantine or post-exposure vaccination. It was the
high vaccination rate in the rest of the community that kept the outbreak from becoming an epidemic.

Christopher Harrison, MD, director of the infectious diseases research laboratory at Children's Mercy Hospitals & Clinic in Kansas City,
Mo., says parents who don't vaccinate may think they are avoiding making a decision that could harm their child.

"They think that if they do nothing it is not their fault; that if they give their child a vaccine and something seems to go wrong, they are going to feel
guilt," Harrison tells WebMD. "But not making a decision is really making a decision, and that decision is to leave your child unprotected. By not
vaccinating, you have really put your child at risk."

"I am a mother of three, age 3 and under, and I see all these mothers blogging about MMR vaccine refusal," she tells WebMD. "This is a story that
needs to be told: Measles is still a threat and the vaccine is very effective. Not vaccinating your children puts them at risk of a lot of complications."

The CDC/San Diego Health Department study appears in the April issue of Pediatrics.

SOURCES:

Sugerman, D.E. Pediatrics, April 2010; vol 125: pp 747-755.

CDC: "Diseases and the Vaccines that Prevent Them."

Burton, Susan. This American Life, "Ruining It for the Rest of Us," Dec. 19, 2008.